地形影响下祁连山北麓不同类型降水特征对比分析

Comparative analysis of different types of precipitation characteristics in the northern foot of Qilian Mountain under the influence of topography

利用张掖CINRAD/CC多普勒雷达资料,结合气象观测资料及L波段探空秒数据,分析祁连山北麓不同类型强降水过程中地形的影响效应,结果表明:不同类型强降水的形成机制及物理量条件各有差异,地形对降水的影响效应也各不相同;各类型降水的大值区集中在山区或山地北坡,地形升高造成的强迫抬升效应显著;局地小地形的阻挡、辐合和抬升作用在强对流性降水过程中较为突出;大地形整体抬升形成的列车效应及局地小地形的汇集作用共同造成了短时强降水型过程;而系统性冷空气影响降水过程中,地形作用的主要表现形式是承载层气流在“口袋”状地形影响下,强回波不断生成并长时间维持;探空数据上,高层冷云降水与低层暖云降水的表征项变化各不相同。

The effects of precipitation on Qilian Mountain and the process of heavy rain in different terrains were evaluated using data from the Zhangye CINRAD/CC Doppler radar,conventional meteorological observation,and L-band second radiosonde.The different types of heavy rain formation mechanisms and physical conditions depend on the effect of terrain on the precipitation.The large value area for every type of precipitation is concentrated in the mountainous area or the northern slope of the mountain.The forced uplift effect caused by terrain elevation was significant.The blocking,convergence,and uplift of minor local terrains are more prominent in the process of strong convective precipitation.The training effect produced by the overall uplift due to the significant topography and the convergence effect caused by the small local topography resulted in a short time heavy precipitation process.In systematic cold air affecting precipitation,the main topographic action form is the strong airflow echo in the bearing layer,which is continuously generating and is being maintained for a long time under the influence of a“pocket”topographic shape.The representational terms of upper-level cold cloud precipitation and lower-level warm cloud precipitation differed in the radiosonde data.